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                <h1>
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                    AJ Utils
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                <h3>Small Java Utils Library</h3>
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                <h3>Common</h3>
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                    <li><a href="/common/JsonUtil/">JsonUtil</a></li>
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                <h1>WebUtils Tutorial</h1>
<p>This tutorial provides an overview of the <code>WebUtils</code> class, which is part of the <code>lightweight-component/aj-util</code> library. The <code>WebUtils</code> class provides utility methods for web-related operations in Java applications.</p>
<h2>Introduction</h2>
<p>The <code>WebUtils</code> class contains static methods for common web operations such as IP address retrieval and cookie handling.</p>
<h2>Main Features</h2>
<ul>
<li>Get local IP address</li>
<li>Get client IP address from HTTP request</li>
<li>Retrieve cookies from HTTP request</li>
</ul>
<h2>Methods</h2>
<h3>1. <code>getLocalIp()</code></h3>
<p>Retrieves the local IP address of the server.</p>
<ul>
<li><strong>Returns:</strong> The local IP address as a String, or null if the address cannot be determined.</li>
</ul>
<p><strong>Example:</strong></p>
<pre><code class="language-java">String ip = WebUtils.getLocalIp();
</code></pre>
<h3>2. <code>getClientIp(HttpServletRequest request)</code></h3>
<p>Retrieves the client's IP address from an HTTP request, handling various proxy headers.</p>
<ul>
<li><strong>Parameters:</strong>
<ul>
<li><code>request</code>: The HttpServletRequest object</li>
</ul>
</li>
<li><strong>Returns:</strong> The client IP address as a String</li>
</ul>
<p><strong>Example:</strong></p>
<pre><code class="language-java">String clientIp = WebUtils.getClientIp(request);
</code></pre>
<h3>3. <code>getCookie(HttpServletRequest request, String cookieName)</code></h3>
<p>Retrieves a cookie value by name from an HTTP request.</p>
<ul>
<li><strong>Parameters:</strong>
<ul>
<li><code>request</code>: The HttpServletRequest object</li>
<li><code>cookieName</code>: The name of the cookie to retrieve</li>
</ul>
</li>
<li><strong>Returns:</strong> The cookie value as a String, or null if the cookie doesn't exist</li>
</ul>
<p><strong>Example:</strong></p>
<pre><code class="language-java">String sessionId = WebUtils.getCookie(request, &quot;JSESSIONID&quot;);
</code></pre>
<h2>Usage Example</h2>
<p>Here's a complete example of using the WebUtils class:</p>
<pre><code class="language-java">import javax.servlet.http.HttpServletRequest;

public class Example {
    public void processRequest(HttpServletRequest request) {
        // Get server IP
        String serverIp = WebUtils.getLocalIp();
        System.out.println(&quot;Server IP: &quot; + serverIp);

        // Get client IP
        String clientIp = WebUtils.getClientIp(request);
        System.out.println(&quot;Client IP: &quot; + clientIp);

        // Get session cookie
        String sessionId = WebUtils.getCookie(request, &quot;JSESSIONID&quot;);
        System.out.println(&quot;Session ID: &quot; + sessionId);
    }
}
</code></pre>
<h2>Conclusion</h2>
<p>The <code>WebUtils</code> class provides simple utility methods for common web operations, making it easier to handle IP addresses and cookies in Java web applications.</p>

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